1. Field of the Invention
The invention relates to a high-voltage MOS transistor device, and particularly, to a high-voltage MOS transistor device having a plurality of first field plate rings. A voltage is applied upon the first field plate rings to maintain a constant electric field within the high-voltage MOS transistor device and prevent breakdown of the high-voltage MOS transistor device.
2. Description of the Prior Art
Current power systems provide an alternating current having a variety of frequencies ranging from 50 to 60 Hz, and a voltage ranging from 100 to 240 volts (V). Every electrical device has a particular working voltage and frequency condition, and therefore, electrical devices and related passive elements utilized in the electrical devices, such as inductors, capacitors, resistors and transformers, act as a switch to determine the value of the voltage and the type of the current thereof. For example, a conventional air conditioner utilizes a power supply providing a low-voltage current for the inner facilities. The power supply switch reduces the voltage provided by the outer power system to an appropriate voltage for the inner facilities. In addition, the power supply switch has the characteristics of high efficiency, low weight, small size and reduced power consumption.
High-voltage metal-oxide semiconductors may function as switches and are broadly utilized in CPU power supplies, power management systems, AC/DC converters, LCD/plasma TV drivers, automobile electronic components, PC peripheral devices, small DC motor controllers, and other consumer electronic devices. The power source supplied by the outer voltage source is an AC power. The usual waveform of an AC power circuit is a sine wave, and a 240V AC power may alter its voltage from −300V to +300V. The voltage may over 600V in an instant. This is greater than the breakdown voltage of most HV MOS transistor devices in the field and leads to HV MOS transistor device damage. Therefore, an HV MOS transistor device capable of withstanding high-voltages is required.